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After reading this question, something occurred to me that I've always wondered - but never thought to ask.

Why are road messages/signs printed in reverse?

enter image description here

(source https://xkcd.com/781/)

Anytime I encounter them, I read them reversed in natural order, and it provides a slight distraction as I flip them around in my head and parse the message. Road signs/messages are short and concise, and always fit into the normal human field of view (e.g. "Llama crossing" instead of "Watch out for the llamas that sometimes wander into the road in this area"). So why would road messages need to be printed in reverse order?

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    The mouse-over text of the comic gives you the answer: "They actually started the reversed-text practice in 1977 -- not for ease of reading reasons, but because too many people were driving backward down the highway blasting the Star Wars opening theme." – clcto May 13 '15 at 22:04
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    Please note that, like literal instead of symbolic street signs, this is a very USsy thing. – Crissov May 14 '15 at 9:52
  • Yeah, totally messes with my head too. I see the bottom part, but skip to the top to read, then it's backwards and I have to work extra hard to flip it around in my head... – Brian Knoblauch May 14 '15 at 20:30
  • Do you know how much govt money has been spent proving that 50.00001% of people prefer this method? And did you know that now the question is being debated by the public that they will have to commission a new 3 year investigation on the original panel's findings? – blankip May 15 '15 at 14:07
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    I suspect that many British people (like me) find it both confusing and amusing to see these in other countries. All British road messages are printed the "right" way (reading top to bottom) - anything else is just weird - and highly distracting. – adelphus May 7 '16 at 17:36
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You read as you approach.

Theoretically. In reality, levels of visual acuity mean that some people (like you and I) can read the whole block at once. Another reason that painting information on the pavement isn't always ideal.

Here's a good visual for how this is designed to function in practice:

"Curve ahead" message designed for high speed reading

The trick is (as the image above shows) the spacing of the lines should be a function of the speed of travel: fast => more distance, slow => less distance. At high speed, this is pretty effective. Slow is a little trickier ...

The slow speed problem

The smaller spacing at low speed is still effective in heavy traffic (where the car in front obscures succeeding lines) and in low visibility conditions like fog where your headlights reveal one line at a time. But the accommodation that makes those important scenarios work also makes for an awkward read when nothing is impeding your vision. It's a trade off.

The Government says so

If you spend any time with the fantastically named FHWA MUTCD you'll see that they don't like to talk about words on pavement. There are reams of paper devoted to standing signs. But there is a not insignificant section on road markings. These are mostly lane indicators and other symbol-based communication.

The most oft spec'd word marking is "ONLY" for use in various lane directions. But there is a small section that speaks to multi-line messages. Here's the actual spec from the FHWA (emphasis mine):

Word and symbol markings should not exceed three lines of information.

If a pavement marking word message consists of more than one line of information, it should read in the direction of travel. The first word of the message should be nearest to the road user.

Trust the researchers

In the end, remember that the US Federal Highway Administration conducts extensive research on these things. That research is hard to find, but I have read of situations where adding pavement markings reduced a given problem (like people careening out of curve).

In most situations, these messages should be a supplement to road signs, which are usually easier to read. In that function, they work pretty well.

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    Yeah - I think this is part of the intent behind the choice, but cognitively it doesn't seem to make a lot of sense. If you cover all but the bottom line of a book page, your instinct isn't to read the page backwards, your instinct is to think "well thats weird - what does the beginning say?". Hoping there's some other functional reason other than this, it just doesn't seem well-thought-out. – CodeMoose May 13 '15 at 21:23
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    You don't read a book as you pass by it at 60 mph either. – plainclothes May 13 '15 at 21:58
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    @CodeMoose you are correct. Ultimately, it's a less-than-ideal situation to write multiple line messages on pavement. But it's the only practical way to read multiple lines when traveling at 60mph. A better approach is usually a sign, where you can have multiple lines of text easily readable from top to bottom. – DA01 May 14 '15 at 2:44
  • @plainclothes touché. – CodeMoose May 14 '15 at 3:45
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    That picture makes a bit more sense - I've never seen the lines spaced out that much before. Usually it's the ever-famous "Ahead stop". +1 – CodeMoose May 14 '15 at 3:49
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In complete agreement with the other answers, but to provide an alternate viewpoint: If you were driving at night, your headlights will reveal the beginning of the sentence before the end.

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    True, that makes sense. I suppose an argument can also be made for heavy traffic, where only one word is visible at a time. Having the words appear from under the car in front of you, one-at-a-time in reverse order, would be frustrating to decode at best. – CodeMoose May 14 '15 at 3:50
5

I have bad vision.

I can see well enough to drive, but if that message is more than a line or two, I won't be able to read the beginning of it before I've passed the end of it.

They're written backwards for me.


Consider the case where you're following a large vehicle, such as a tractor trailer that prevents you from seeing subsequent lines. It would be difficult to understand when you're only able to see one line at a time if the lines aren't in order.


Additionally, it's important to consider other drivers who may have trouble reading. It's necessary to give everyone the maximum possible time to see and read signage.

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    Um sorry but if your vision is so bad that you cannot see three lines of road markings in front of you, how on earth can you "see well enough to drive"??? – Lightness Races in Orbit May 14 '15 at 10:38
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    This question is not about the extreme case in that image (which only an answerer dug up). From the question: "Road signs/messages are short and concise, and always fit into the normal human field of view". It's these messages you're answering about, so if you can't see them (potentially with glasses) then you shouldn't be driving at all. – Lightness Races in Orbit May 14 '15 at 14:19
  • @LightnessRacesinOrbit, i've updated my answer to clarify my intent. It's not so much about seeing the text as being able to discern what it says. – zzzzBov May 14 '15 at 14:22
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    @LightnessRacesinOrbit There is a difference between being able to read one short word and reading several short words printed right on top of each other on the road at 60mph. My (uncorrected) vision is good enough where I can figure out one unfamiliar (as in I've never seen that particular road sign so I don't have built in experience to guestimate what it says) in that time, but not several. Should I not be able to drive? In any case, I am allowed drive (uncorrected) so perhaps you may consider you've misunderstood "normal human field of view". – iheanyi May 6 '16 at 18:59
3

It facilitates reading the text in moderate traffic.

If there are other vehicles on the road and you are following at a safe distance, you will read the closer text first as your view of the farther text will be blocked. This allows you to read the full message incrementally.

Obviously this breaks down when there is no traffic and you have decent vision, but seeing the full message is a feature, not a bug in this case.

0

This is a means to address the smallest minority of drivers who have difficulty reading. Fluent readers will "chunk" the phrase, even if separated into two lines. E.g., you understand, "Stop Ahead" as one concept or action, and find "AHEAD STOP" as awkward or odd. Although there may be some research done on this subject, it may have been poorly-framed. It is also not clear that pavement words are effective at all, or more effective than lines and symbols.

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